1. Field of the Invention
The present invention relates to a microphone unit having a microphone held in a rubber holder, and to the holder used in the microphone unit.
2. Description of the Related Art
Japanese Patent No. 3,244,448 discloses a small-size microphone mounted in a cellular phone. The microphone has an outer circumferential surface substantially cylinder-shaped, and a lower end surface on which a ground terminal and a plus terminal are disposed. The ground and plus terminals are provided so as to be electrically connected to electrically conductive patterns on a board (hereinafter referred to as “external board”) in the cellular phone.
The microphone is mounted on the external board while the microphone is held in a rubber holder so as to be substantially cylindrically covered with the rubber holder for the purpose of prevention of sound leakage, positioning, etc.
Reduction in microphone size has advanced in recent years, and a microphone having a diameter of not larger than 3 mm has been developed. In such an ultra small microphone, a space for arranging a ground terminal and a plus terminal has been hardly ensured on a lower end surface of the microphone.
In order to mount the microphone on the board without consciousness of the directivity of the microphone, it is preferable that a terminal arrangement called bull's eye (i.e., a terminal arrangement in which the ground terminal and the plus terminal are arranged concentrically) is adopted. It is however difficult to ensure a sufficient gap between the two terminals if the outer diameter of the microphone becomes smaller than a certain value. This causes a problem that steady electric connection of the terminals to electrically conductive patterns of the external board respectively can be hardly attained when the microphone is mounted on the external board.
Therefore, in the conventional ultra small microphone, one end portion of a lead wire need be soldered to each of the ground terminal and the plus terminal in advance, and the other end portion of the lead wire need be soldered to each of electrically conductive patterns of the external board when the microphone is mounted on the external board. This causes a problem that efficiency in mounting the microphone is very low.